Note that the default huge page size is either 2 or 4 MiB, depending on the platform. Also mention /sys/kernel/mm/hugepages/ as another place to see the supported huge page sizes. Signed-off-by: Vincent Fu <vincent.fu@xxxxxxxxxxx> --- HOWTO.rst | 25 ++++++++++++++----------- fio.1 | 19 ++++++++++--------- 2 files changed, 24 insertions(+), 20 deletions(-) diff --git a/HOWTO.rst b/HOWTO.rst index eee386c1..58d02fa2 100644 --- a/HOWTO.rst +++ b/HOWTO.rst @@ -1823,13 +1823,14 @@ Buffers and memory **mmaphuge** to work, the system must have free huge pages allocated. This can normally be checked and set by reading/writing :file:`/proc/sys/vm/nr_hugepages` on a Linux system. Fio assumes a huge page - is 4MiB in size. So to calculate the number of huge pages you need for a - given job file, add up the I/O depth of all jobs (normally one unless - :option:`iodepth` is used) and multiply by the maximum bs set. Then divide - that number by the huge page size. You can see the size of the huge pages in - :file:`/proc/meminfo`. If no huge pages are allocated by having a non-zero - number in `nr_hugepages`, using **mmaphuge** or **shmhuge** will fail. Also - see :option:`hugepage-size`. + is 2 or 4MiB in size depending on the platform. So to calculate the + number of huge pages you need for a given job file, add up the I/O + depth of all jobs (normally one unless :option:`iodepth` is used) and + multiply by the maximum bs set. Then divide that number by the huge + page size. You can see the size of the huge pages in + :file:`/proc/meminfo`. If no huge pages are allocated by having a + non-zero number in `nr_hugepages`, using **mmaphuge** or **shmhuge** + will fail. Also see :option:`hugepage-size`. **mmaphuge** also needs to have hugetlbfs mounted and the file location should point there. So if it's mounted in :file:`/huge`, you would use @@ -1848,10 +1849,12 @@ Buffers and memory .. option:: hugepage-size=int - Defines the size of a huge page. Must at least be equal to the system - setting, see :file:`/proc/meminfo`. Defaults to 4MiB. Should probably - always be a multiple of megabytes, so using ``hugepage-size=Xm`` is the - preferred way to set this to avoid setting a non-pow-2 bad value. + Defines the size of a huge page. Must at least be equal to the system + setting, see :file:`/proc/meminfo` and + :file:`/sys/kernel/mm/hugepages/`. Defaults to 2 or 4MiB depending on + the platform. Should probably always be a multiple of megabytes, so + using ``hugepage-size=Xm`` is the preferred way to set this to avoid + setting a non-pow-2 bad value. .. option:: lockmem=int diff --git a/fio.1 b/fio.1 index ded7bbfc..5f057574 100644 --- a/fio.1 +++ b/fio.1 @@ -1631,11 +1631,11 @@ multiplied by the I/O depth given. Note that for \fBshmhuge\fR and \fBmmaphuge\fR to work, the system must have free huge pages allocated. This can normally be checked and set by reading/writing `/proc/sys/vm/nr_hugepages' on a Linux system. Fio assumes a huge page -is 4MiB in size. So to calculate the number of huge pages you need for a -given job file, add up the I/O depth of all jobs (normally one unless -\fBiodepth\fR is used) and multiply by the maximum bs set. Then divide -that number by the huge page size. You can see the size of the huge pages in -`/proc/meminfo'. If no huge pages are allocated by having a non-zero +is 2 or 4MiB in size depending on the platform. So to calculate the number of +huge pages you need for a given job file, add up the I/O depth of all jobs +(normally one unless \fBiodepth\fR is used) and multiply by the maximum bs set. +Then divide that number by the huge page size. You can see the size of the huge +pages in `/proc/meminfo'. If no huge pages are allocated by having a non-zero number in `nr_hugepages', using \fBmmaphuge\fR or \fBshmhuge\fR will fail. Also see \fBhugepage\-size\fR. .P @@ -1655,10 +1655,11 @@ of subsequent I/O memory buffers is the sum of the \fBiomem_align\fR and \fBbs\fR used. .TP .BI hugepage\-size \fR=\fPint -Defines the size of a huge page. Must at least be equal to the system -setting, see `/proc/meminfo'. Defaults to 4MiB. Should probably -always be a multiple of megabytes, so using `hugepage\-size=Xm' is the -preferred way to set this to avoid setting a non-pow-2 bad value. +Defines the size of a huge page. Must at least be equal to the system setting, +see `/proc/meminfo' and `/sys/kernel/mm/hugepages/'. Defaults to 2 or 4MiB +depending on the platform. Should probably always be a multiple of megabytes, +so using `hugepage\-size=Xm' is the preferred way to set this to avoid setting +a non-pow-2 bad value. .TP .BI lockmem \fR=\fPint Pin the specified amount of memory with \fBmlock\fR\|(2). Can be used to -- 2.25.1
